Bohol’s Tarsiers – the smallest monkey in the world?

Another goal of our project in the Philippines was the tarsiers reservation of the Bohol island. Tarsier is a primate that is related to Lemurians and has been promoted as the smallest monkey in the world.

Tarsiers (Tarsius syrichta) on the island of Bohol is monitored and protected by the Philippine Tarsier Foundation.

Tarsiidae is the only family in the genus Tarsius. There are 7 extant species of tarsiers, all similar in size, morphology, and ecology. They are all small, nocturnal, carnivorous primates specialized for leaping and clinging. Tarsiers are the most “primitive” of the haplorhine primates, with fossils dating to the Eocene. They were once widely distributed, fossils are known from North America, Europe, North Africa, and Asia (Niemitz, 2003).

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Tarsier species are all highly arboreal and are found primarily in tropical, forested habitats with dense vertical growth. They use “vertical clinging and leaping” between tree trunks or other vertical supports extensively while locomoting (Niemitz, 2003). Tarsiers are small primates, weighing 80 to 150 g. Their fur is velvety or silky and buff, grayish brown, or dark brown on the back and grayish or buffy on the underside, generally resembling the color of dead leaves or bark. Their most distinctive features are their round heads, remarkably large eyes that are directed forward, and their medium to large, hairless, and very mobile ears (Feldhamer et al., 1999; Groves, 1989; Niemitz, 2003).

The most noticeable thing about tarsiers are their eyes. They have the largest eyes relative to body size of any mammal. Each eyeball is around 16 millimeters in diameter, which is as large as the tarsier’s entire brain, but every last millimeter is necessary since the tarsier is a nocturnal species. The eyes are so large, they can’t rotate them, so they have a neck that do the work instead. Tarsiers can rotate their necks a full 180 degrees in either direction, just like owls.

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Tarsiers are the only entirely carnivorous primate. While the specific diet varies with the species, they all have one thing in common: they don’t eat plant matter of any kind. They feast on insects, reptiles like lizards and snakes, frogs, birds and even bats. While small and cute, they’re serious ambush predators, waiting silently for prey to approach nearby — and can even snag birds and bats right out of the air.

The Philippine tarsier is nocturnal; they hunt at night, exclusively for animal prey. At day time, they hide in hollows close to the ground. When kept in captivity, individuals may huddle together or intertwine their tails. They are believed to live in groups, larger than just one male and one female. The female appears to take care for the young exclusively: no male parental care has been observed.